Here's an outline of how I see __main__.__spec__ playing out relative to the various cmdline interfaces. == == == === ==== ======== ======== ======== ======== ============ - -c -m dir file name loader origin cached has_location == == == === ==== ======== ======== ======== ======== ============ __main__ builtin - None False X __main__ builtin - None False X __main__ builtin -c None False X (finder) (finder) (finder) (finder) (finder) X __main__ <loader> path None True X __main__ <loader> path None True == == == === ==== ======== ======== ======== ======== ============ Note: __main__.__spec__ in the -m case is addressed in issue #19700. Thoughts? See: [1] http://docs.python.org/3.4/using/cmdline.html [2] Python/pythonrun.c [3] Modules/main.c